DistributionEditor: set lower bound for mean spinbox

This MR resolves #473 (closed)

The mean value of wavelength distributions cannot be set to less than the value double::min anymore in the DistributionEditor.

GUI/View/Instrument/DistributionEditor.cpp

@@ -126,7 +126,6 @@ void DistributionSelector::createMeanSpinBox(DoubleProperty& d)
     if (m_meanConfig) {
         if (m_meanConfig->scientific) {
             auto* sb = GUI::Util::createScientificSpinBox(m_formLayout, d);
-            sb->setMinimum(std::numeric_limits<double>::min());
             connect(sb, &ScientificSpinBox::valueChanged, [this, &d](double v) {
                 d.setValue(v);
                 emit distributionChanged();